The present invention relates to implantable electrical leads generally, and more specifically to cardiac pacing leads.
The conductors in cardiac pacing leads occasionally have a tendency to fracture due to repetitive application of stress to the conductor. One way in which this problem has previously been addressed is by reinforcing the lead body in the area in which stress is to be expected, as in U.S. Pat. No. 5,545,203, issued to Doan et al. This patent is directed primarily toward reinforcing the lead against fracture due to application of compressive forces. Reinforcement of the lead body is also disclosed in U.S. Pat. No. 5,591,142, issued to Van Erp et al. It has also been proposed to reinforce the lead body by means of adding a tensile reinforcement as in U.S. Pat. No. 5,231,996 issued to Bardy et al. In this patent, the lead is provided with a nonconductive tensile member such as a polyester cord, which runs the length of the lead body. Other leads having cords or reinforcements running throughout their length are disclosed in U.S. Pat. No. 3,844,292 and U.S. Pat. No. 3,572,344 issued to Bolduc. A third proposal for dealing with the possibility of conductor fracture is to render the portion of the lead body in direct contact with the conductor conductive by addition of carbon or other conductive material, as disclosed in U.S. Pat. No. 4,033,355, issued to Ammundson.